[嵌入式]STM32 LWIP SNTP实现毫秒级的时间校准

1、首先配置LWIP支持SNTP

?然后在opt.h中增加一个timeout->LWIP_SNTP?

防止出现类似

Assertion "sys_timeout: timeout != NULL, pool MEMP_SYS_TIMEOUT is empty" failed at line 190 in ../Middlewares/Third_Party/LwIP/src/core/timeouts.c

这样的错误。

/**
 * The number of sys timeouts used by the core stack (not apps)
 * The default number of timeouts is calculated here for all enabled modules.
 */
#define LWIP_NUM_SYS_TIMEOUT_INTERNAL   (LWIP_TCP + LWIP_SNTP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + PPP_NUM_TIMEOUTS + (LWIP_IPV6 * (1 + LWIP_IPV6_REASS + LWIP_IPV6_MLD)))

在使用sntp之前，需要对其进行初始化，初始化放在lwip初始化之后就行了。

void set_sntp_server_list(void)
{
	uint32_t server_list[SNTP_MAX_SERVERS] = {0x9f64a8c0}, // 我本地windows创建的NTP服务器,192.168.100.159
	ip_addr_t sntp_server;
    // 本身支持多个服务器，我们这里SNTP_MAX_SERVERS = 1								
	for(int i = 0; i < SNTP_MAX_SERVERS; i++)
	{
		sntp_server.addr = server_list[i];
		sntp_setserver(i, &sntp_server);
	}
}

void dev_sntp_init(void)
{
	sntp_setoperatingmode(SNTP_OPMODE_POLL);
	sntp_init();
	set_sntp_server_list();
}

2、在使用LWIP进行嵌入式程序开发时，实现秒级的时间校准，只需要重新定义SNTP_SET_SYSTEM_TIME(sec)这个函数就可以了。

#define SNTP_SET_SYSTEM_TIME		sntp_set_time

void sntp_set_time(time_t sntp_time)
{
	if(sntp_time == 0)
	{
		return;
	}

	struct tm *time;
	sntp_time += (8*3600); // 时区
	time = localtime(&sntp_time);
    printf("%d:%d:%d\r\n", time->tm_hour,time->tm_min,time->tm_sec);
    printf("%d:%d:%d\r\n", time->tm_year+1900,time->tm_mon+1,time->tm_mday);
}

3、参考sntp_otp.h中的介绍：

/** SNTP macro to change system time in seconds
?* Define SNTP_SET_SYSTEM_TIME_US(sec, us) to set the time in microseconds
?* instead of this one if you need the additional precision. Alternatively,
?* define SNTP_SET_SYSTEM_TIME_NTP(sec, frac) in order to work with native
?* NTP timestamps instead.
?*/

只需要重新实现SNTP_SET_SYSTEM_TIME_US(sec, us)这个函数就可以了。

#define SNTP_SET_SYSTEM_TIME_US     sntp_set_timeus

void sntp_set_timeus(time_t sntp_time, int us)
{
	if(sntp_time == 0)
	{
		return;
	}

	struct tm *time;
	sntp_time += (8 * 3600); // 时区
	time = localtime(&sntp_time);
    printf("%d:%d:%d.%d\r\n", time->tm_hour,time->tm_min,time->tm_sec, us);
    printf("%d:%d:%d\r\n", time->tm_year+1900,time->tm_mon+1,time->tm_mday);
}